1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer, copying machine, and facsimile, and in particular, relates to an image forming apparatus using a removable toner container and capable of replacing toner.
2. Description of the Related Art
In an image forming apparatus such as a printer, copying machine, and facsimile, an image is formed by an electrophotography system, offset printing system, inkjet printing system or the like. In addition, as an example of such an image forming apparatus, an image forming apparatus capable of forming a color image by the electrophotography system has been known. Mainly from a structure viewpoint, such an image forming apparatus has an image formation part including a plurality of image formation units and is classified into either a tandem system in which the plurality of image formation units is arranged in a line or a rotary system in which the plurality of image formation units is arranged in a cylindrical shape. Also, the transfer methods are classified into a direct transfer method by which a toner image is directly transferred from a photosensitive member to a sheet and an intermediate transfer method by which a toner image is temporarily transferred to an intermediate transfer member before being transferred to a sheet. The intermediate transfer tandem system in which a plurality (four) of image formation units is arranged on an intermediate transfer belt need not hold, like the direct transfer method, sheets on a transfer drum or transfer belt. Thus, the intermediate transfer tandem system has an advantage from the viewpoint of capability of dealing with various kinds of sheets such as a super-cardboard and coat paper. Further, a paper path up to a secondary transfer unit can be simply structured and the stretching method of the intermediate transfer belt is highly flexible. Therefore, the intermediate transfer tandem system has also an advantage in miniaturization of the image forming apparatus.
On the other hand, in consideration of the environment problem, various techniques have been discussed to use up toner in a toner container in an image forming apparatus (see, for example, Japanese Patent Application Laid-Open No. 2004-271956). Japanese Patent Application Laid-Open No. 2004-271956 discusses an image forming apparatus that detects the remaining amount of toner in a plurality of toner containers containing toner and moves a toner container found to be substantially out of toner to a replacement position by a movable member, which makes the toner container replaceable. Moreover, the image forming apparatus is configured such that if there is a plurality of toner containers found to be out of toner, the toner container that is to be preferentially moved to the replacement position is selected.
However, further improvements are desired regarding the conventional technique described above. More specifically, the toner container at the replacement position can be extracted at any moment and if a toner container that is not used up is at the replacement position, the toner container has been freely replaced. Moreover, only the toner container at the replacement position can be replaced. Therefore, if there is a plurality of toner containers found to be out of toner, an operation to move another toner container to the replacement position has been necessary.